This application relates to magnetic disc drives and more particularly to an apparatus for increasing operational wind force on a latching device for latching a disc drive actuator mechanism in a parked position when the drive is de-energized.
Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium on a disc. Modern disc drives comprise one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (xe2x80x9cheadsxe2x80x9d) mounted to a radial actuator for movement of the heads relative to the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g. a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment. Critical to both of these operations is the accurate locating of the head over the center of the desired track.
The heads are mounted via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs.
Typically, such radial actuators employ a voice coil motor to position the heads with respect to the disc surfaces. The actuator voice coil motor includes a coil mounted on the side of the actuator body opposite the head arms so as to be immersed in the magnetic field of a magnetic circuit comprising one or more permanent magnets and magnetically permeable pole pieces. When controlled direct current (DC) is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body pivots about the pivot shaft and the heads move across the disc surfaces. The actuator thus allows the head to move back and forth in an arcuate fashion between an inner radius and an outer radius of the discs.
When the drive is de-energized or shut down, the drive motor stops spinning and the actuator is rotated, for example, counterclockwise to position the heads at an inner diameter landing zone location and latch the actuator in this position. Often a magnetic latch is used to maintain the actuator in this position with the heads in the landing zone. When a magnetic latch is used, an inadvertent external shock load, such as the drive being dropped, may cause sufficient rotational force to be applied to the actuator arms to overcome the magnetic attraction and thus the actuator arm may rotate from the landing zone to the data region of the discs without the discs spinning at all. This could destroy the stored data and could destroy the heads themselves. Consequently there is a need for a latch mechanism that ensures that the actuator stays in the parked position any time that the disc drive motor is de-energized and, more importantly, the discs are not spinning.
This de-energized latching has been traditionally accomplished by a wind operated latching mechanism which utilizes wind generated by the spinning discs while the drive motor is energized to push against a pivoting air filter member positioned adjacent the outer margin of the discs. This air filter member has a pivot portion, an air filter portion, and an elongated air vane which extends outward from the air filter portion over the top disc in the disc stack. The air vane is directly in the path of air drawn along the surface of the disc by the rotating disc. This moving air is a wind which pushes against the air vane, tending to rotate the air filter member about its pivot in a clockwise direction as viewed from above. Extending from the opposite side of the pivot portion of the air filter member is an elongated latch arm and a tab portion which carries a steel ball therein. The steel ball in the tab portion is positioned in the magnetic field generated by the VCM magnets and thus biases the latch on a counterclockwise direction such that the latch arm interferes with rotational movement of the actuator arm off of the magnetic latch when the drive is de-energized.
The operation of this conventional latch mechanism is completely automatic, driven only by the VCM magnet magnetic field bias and the force exerted by wind against the air filter and the air vane when the discs are spinning at normal speed. The size and placement of the steel ball on the tab portion are dictated by the requirement that the latch be disengaged when the discs are operating at full speed and engaged when the discs are turning at less than full operating speed with the actuator arm moved into the parked position.
The conventional air vane design has worked well for drives with three or four or more operating discs in the head disc assembly (HDA). However, in the case of drives designed for four discs and having only one or two discs installed, there have been cases where the air vane latches failed to move to the disengaged position when the drive is energized, thus preventing actuator movement and appearing to the user by the software as a disc crash or disc drive failure. In these cases, the failures appear to have occurred at high altitudes. Accordingly, there is a need for a magnetic wind operated latching apparatus for use in disc drives having only one or two discs which automatically disengages the actuator arm when the disc drive motor spins the discs at operating speed and engages the actuator arm when the disc or discs spin at less than operating speed and the actuator arm is in the parked position in a head disc assembly (HDA) designed to accommodate up to four or more discs.
Against this backdrop the present invention has been developed. The present invention is a stationary air vane member adapted to be fastened to a disc drive baseplate beneath a single spinning disc in a HDA designed to carry two or more discs on the drive motor spindle. The air vane member acts to accelerate wind which is generated by the rotating disc in the HDA and direct it to a pivoting air filter which typically has an air vane which extends over the upper surface of a top disc on the disc drive motor. This arrangement provides an additional moment arm on the pivoting air filter when only one disc is located on the drive motor in the HDA. This stationary air vane provides a narrowing channel beneath the spinning disc directing wind generated by the spinning disc toward the air filter portion of the latch member thus capturing additional air flow and thus providing an additional moment arm on the air filter latch when the drive is utilized at high elevations where the air is thinner. This stationary air vane member may also permit a larger steel ball to be utilized in the conventional latch apparatus thereby ensuring more positive latch and unlatch operations of the apparatus.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.